x(15-4.9x)=0

Solution for x(15-4.9x)=0 equation:

x(15-4.9x)=0

We add all the numbers together, and all the variables

x(-4.9x+15)=0

We multiply parentheses

-4x^2+15x=0

a = -4; b = 15; c = 0;
Δ = b2-4ac
Δ = 152-4·(-4)·0
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-15}{2*-4}=\frac{-30}{-8}
=3+3/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+15}{2*-4}=\frac{0}{-8}
=0
$